Though the harbor's overall grade for 2013, to be released Wednesday, is down from a C-minus the year before, the city's signature water body didn't actually get more polluted last year, according to organizers of the Healthy Harbor campaign.

Instead, the harbor campaigners said they've just decided to stop grading on a curve and deliver a more straightforward assessment — that it's far from safe to swim or splash around in the trash- and sewage-fouled upper reaches of the Patapsco River.

"We recognize that it was confusing for folks to see a C-minus while the grades were essentially under 50 or around 50 percent — which everyone knows is not passing," said Halle Van der Gaag, executive director of Blue Water Baltimore, one of the groups behind the report card. "We felt it was important to tell the story accurately."

The Healthy Harbor campaign aims to make the water fishable and swimmable by 2020, a goal campaigners acknowledge is "ambitious." The campaign is a collaboration between the Waterfront Partnership, a business-led group, Blue Water Baltimore, a nonprofit environmental group, Baltimore City and Baltimore County.

Baltimore's harbor, the lower Patapsco River and the streams that feed into it earned water-quality scores last year ranging from 51 percent to 57 percent, up from 41 percent in 2012. The water remains murky, though, and polluted with trash, sewage and other wastes, which under certain conditions can feed algae blooms and cause fish kills. The Inner Harbor and Middle Branch also have unsafe levels of bacteria much of the time.

The pollution and trash doesn't stop at the harbor, this report card reveals. Expanded water-quality monitoring has found that the streams flowing into the harbor from Baltimore County are in poor shape as well, with high levels of bacteria and nutrient pollution.

"It's a wake-up call," Van der Gaag said of the failing grades. "We've got to move forward faster, get more work done."

While sewage overflows declined by more than 90 percent, David Flores, the harbor waterkeeper, said chronic leaks from aging sewer lines in the city and Baltimore County are the likely culprits in chronically high bacteria levels in the water.

Adam Lindquist, with the Waterfront Partnership, said despite the poor grades, he's optimistic that cleanup efforts are gaining steam — though he said he'd like to see more from the city on how it intends to spend the $25 million a year it's projected to raise in stormwater management fees.

The city is in the throes of a $900 million court-ordered program to fix sewage overflows, financed through monthly water and sewer charges that also have risen in recent years. Jeffrey Raymond, spokesman for the Department of Public Works, provided a summary of seven projects the city expects to launch this year to capture and treat polluted stormwater runoff and to keep trash out of storm drains.

"The F grade tells us how far we still must go, but there is real progress being made in a long-term commitment to cleaning Baltimore's waterways and creating a healthier city," Raymond said.

A "water wheel" designed to scoop up 50,000 pounds of flotsam every day debuts Thursday in the channel between Piers 5 and 6, where the Jones Falls empties into the Northwest Branch of the Patapsco River.